The broad goal of the proposed research is to unravel the mechanisms whereby alcohol and cocaine induce stroke. In this regard, we have reported that alcohol and cocaine provoke severe cerebrovasospasm and rupture of cerebral microvessels which seem to be set into motion by a loss in brain cytosolic free magnesium ions ([Mg2+]1) and alterations in cellular bioenergetics. The specific aims of the proposal, using non- invasive in-vivo biophysical techniques as well as cell cultaure techniques of barrier cells, molecular fluorescent probes, patch-clamping of single brain cells, and high-resolution in-situ quantitative TV-image intensification, are to test the following hypotheses: 1. Dietary manipulation in Mg intake will alter the responsiveness of the cerebral microvessels to administration of vasculotoxic doses of alcohol and cocaine HCI. 2. Alcohol and cocaine-induced cerebrovasotoxicity in the rat brain occurs by virtue of a loss of cellular Mg2+ coupled with disturbances in cellular bioenergetics. 31Phosphorous-nuclear magnetic resonance spectroscopy (31P-NMRS) in-vivo will be used to assess intracellular free Mg2+, cytosolic phosphocreatine (PCr), cytosolic adenosine triphosphate (ATP), cytosolic inorganic phosphate (Pi) and intracellular pH([H+]i). Surface reflectance spectroscopy (SRS) will be used to measure the mitochondrial level of reduced cytochrome oxidase aag, deoxyhemoglobin in blood, and blood content. 3. Low dietary intake of Mg results in loss of brain[Mg2+]i concomitant with elevation in brain Ca content, and alcohol or cocaine exacerbates these changes in divalent metal levels. 4. Using single cultured cerebral vascular smooth muscle cells, brain capillary endothelial cells, and astrocytes-type 2 cells, and molecular fluorescent probes (employing spatial, digital image microscopy) for [Ca2+]i, [Mg2+]o and [Ma+]i, as well as 31P-NMRS, test the hypothesis that chronic alcohol and cocaine result in concentration-dependent deficits in intracellular free Mg2+, [PCr] as well as elevations in [Ca2+]i, [Na+]i and [Pi]. 5. Chronic administration of alcohol and high doses of cocaine result in: (a) progressive loss of brain [Mg2+]i followed by progressive losses in [PCr] and [ATP] as well as intracellular acidosis, (b) progressive constriction of cerebral arterioles and venules with a higher than normal incidence of rupture of these cortical microvessels followed by bleeding. 6. Cerebrovasospasm produced by alcohol and cocaine is: (a) set into motion by rapid loss of [Mg2+]i which then activates protein kinase C (PKC) to promote contraction. Cultured cerebral vascular smooth muscle cells will be used to assess the effects of acute and chronic alcohol and cocaine exposure on PKC and IPs activity. 7. Low voltage Mg2+-regulated Ca2+ ion channels in brain capillary endothelial cells are altered by alcohol and cocaine. 8. Alcohol and cocaine cause cerebrovasospasm by acting, in part, upon excitatory amino acid receptors, e.g., N-methyl-D-aspartate (NMDA) type of receptors, which are regulated by Mg2+.